Application of a Ring Pseudorandom Aperture for Transverse Section Tomography

Tomographic images of gamma ray sources have been obtained by the use of a one-dimensional pseudorandom aperture and computerized digital reconstruction. The binary code is laid out on the surface of a cylinder. The source to be imaged must be located within the cylinder and detectors are placed outside and facing inward. The length of the code is matched to the cylinder circumference so that its rotation provides a complete pseudorandom time modulation for each source-detector combination. Counts from each detector are separately stored as a function of the rotation phase angle. Subsequent correlation computations give the reconstructed source intensity along any angle within the fan for each detector. Experimentally measured variances confirm the predictions of a theoretical analysis of the statistics of pseudorandom imaging given elsewhere. We have used only three detectors to date, but the scheme will easily accommodate a complete detector ring to maximize the photon counting efficiency and permit a full tomographic reconstruction of the section.